Rain Man's Brain Explained

Autistic children can mimic faces, but they can't read expressions.

Mirella Dapretto, a neuroscientist at the University of California at Los Angeles, may have nailed down the source of some of autism's key symptoms, the social and emotional deficits that make it so difficult for autistic people to interact with others.

Dapretto and her colleagues showed autistic children pictures of human faces, each photo conveying an emotion like happiness or fear, and asked them to imitate what they saw. The researchers scanned the children's brains as they performed the task and compared the results with those of children who were developing normally.

The children in the normal-development group displayed heightened activity in a number of brain regions, but two spots were of particular interest: the movement center (associated with changing facial expressions) and an area near the front of the brain that includes the mirror-neuron system. Mirror neurons are brain cells that fire both when we perform an action and when we watch someone else do it. "They're connected to emotion centers in the brain and are what allows us to empathize with other people," Dapretto says.

Autistic children exhibited similar activity in their brains' movement centers, but function in the mirror-neuron centers was conspicuously low. And the more severe a child's social impairment was, the weaker the activity in the brain's mirror region. "The kids were doing the task, but they weren't doing it in a way that allowed them to feel what the other person felt," says Dapretto. She hopes this finding will inspire new therapies for autistic children: "If you have an intervention that jumpstarts this system—if you can get a child to think, 'Hey, that's the face I feel when I'm angry'—in the long run you should see improvement."